~ Restoration, modification and servicing of wristwatches

WYSIWYG: A Seiko 7548-700B

Genuine. Straight. Honest. Three words that should foster a sense of confidence that a transaction you are about to embark upon is one in which you can trust that what you see in your object of desire is what you expect to get. Perversely, the greater the sense that what you see is something sitting rather closer to perfection than basket case, the more likely you are to be disappointed. In the world of used watch online auctions and sales, in my book, any impression that something has been gussied up increases the likelihood that the gussying is there to delude, to deceive, to pull the wool over your eyes. This is why I tend, on the whole, to look for watches that have been used until they have been set aside, preferably for the sort of everyday reasons one would usually set something aside (compromised function or changing priorities or tastes). In many cases it is obvious why they have been set aside, in others not so much, but the common denominator with such watches when you can find them is that they simply are what they are.

This does not mean however, that one should buy junk. No. What you have to do is to tip toe a path through the junk, the gussied and much of the stuff pedaled by dealers and traders, and sniff out watches being sold by private individuals. Above all, never buy from anyone who claims to be selling a watch from their own private collection; never buy from anyone who wears white cotton gloves; and never, ever buy from anyone who sells Seiko 6309’s fitted with SCUBAPRO dials or indeed refers to them as Turtles. With that minor little rant out of my system, let’s meet our honest John specimen: a bezel-less, grubby, and apparently broken Seiko 7548-700B.

In what sense can I possibly be accused of entering into a transaction expecting anything other than what appears to be on display? The aspects of the appearance of the watch that fostered confidence were the dirt around the crystal retaining ring which suggested the crystal had never been changed, the presence of a click ball, obviously original hands, a case showing original lines and a dial and hands that appear largely free from corrosion. In one of the photos it was evident that some of the markers on the dial were dirty, but they did not appear degraded. So in went my modest, but not too modest, bid and the watch was mine. An extra £2.80 for postage, a three day wait and it was in my hands.

The absence of the bezel ring was not a worry because I have at least three tucked away but the insert would require a little thought and some modest expense. With the watch in hand and my chosen bezel ring selected and test fitted to make sure the lip on the case is not too worn, we can appraise the watch.

The case back reports the watch to have emerged from the Suwa factory in August 1981, with battery changes noted in 1984 and in 1990. The crystal shows obvious signs of its age but the dial and hands are excellent, only marred slightly by some debris sitting on the dial surface and dirt around the edges of many of the markers. Happily, the crown and crown tube appear to have their full complement of thread and the crown screws in nicely with three and a half to four good twists.

The watch came without a battery but I don’t need to fit a fresh one to confirm this as a non-runner:

It is clear that there has been a major electrolyte leakage from a silver oxide battery in the past, clearly contaminating much of the main plate on this side, and which has resulted in the growth of what I deduce must be copper II hydroxide crystals adjacent to the negative terminal.

On a brighter note, a better view of the dial unobscured by the battered crystal does not change my initial assessment. Some tentative buffing of one or two of the markers with some microfinishing film suggests that the dirt can be removed without too much bother.

With the hands detached from their posts but still in place, we can see that they are tarnished but otherwise in excellent condition. Again, I suspect that they will clean up nicely.

Having removed the dial and hands, it becomes clear that the battery leakage was not confined to the battery side of the movement.

Even the dial guards have been contaminated which does not bode well for the circuit and coil, both of which more directly in the firing line. The underside of the circuit bock reveals the truth of that concern:

Not only is much of the circuitry affected, but the oscillator circuit is overrun which causes some concern that the circuit block may not be salvageable. A minor diversion at this point in proceedings was the pleasure in noting the beautiful crystalline copper salt architectures that had developed on this side of the block, having had free reign to bloom in the extended period in which the compromised battery had clearly had to do its worst.

The extent to which the movement will have been swimming in sodium hydroxide is clear from the contamination of the train wheel bridge, rotor stator and much of the surface of the main plate in the vicinity of the battery location.

In spite of the evidently compromised state of the electrical components, the moving parts and main fabric of the movement ought to clean up satisfactorily and so I pressed on to the cleaning stage. Some of the salts and crystallised electrolyte will not dissolve in the cleaning fluid though and so some elbow grease will also be needed to expunge most of the remaining traces of contamination.

Reassembling the movement proved straightforward enough, with the only minor fiddle being the location and securing of the reset lever. The lever is set initially with the crown pulled out to the second position, the sprung part located around its pin, the screw tightened down and the crown depressed again. You can see the sequence, more or less in the animated gif below.

There is probably not much served in recounting the reassembly in detail because we’ve covered this movement before but it is worth taking a quick gander at the cleaned under underside of the circuit block.

This doesn’t look too bad all things considered and so let’s press on, optimism having reigned in presuming that my efforts to expunge errant NaOH and colourful copper salts will have magically restored function.

A fresh battery inserted and ….

…nada. Not a twitch. Oh dear. Well, the good news is that it can only be one of two things: the circuit block or the coil. I have potential replacements for both resting in the clearly functioning innards of a sacrificial 7546. First though, I try the cleaned circuit block from my 7548 in the 7546 and it springs into life which suggests that counter to appearances, it is the clean looking coil that succumbed to the attentions of the electrolyte rather than the circuit block. So my attention turns to the 7546 coil.

Happily, with replacement part in position, the 7548 lives once more and we can press on with the rest, starting with the calendar side.

With the day disk fitted and all of the calendar functions tested, the dial and hands can be refitted, the latter having been spruced up and now largely free from tarnish.

Attention now turns to the case. Essentially sound in all departments, it only needs a good clean and a fresh crystal.

Here it is freshly scrubbed with the chapter ring, spacer and crystal gasket in position, ready to receive the new crystal.

The crown, as is typically the case with these old 150m divers, needed a fresh gasket which requires it to be dismantled into its constituent parts.

Getting the old gasket out is generally straightforward, but refitting a fresh one, particularly with the stem post still in position can be a somewhat fraught exercise. In goes the movement, crown & stem, movement spacer with spring and we are set fair to fit a fresh case back gasket, close her up and prepare to fit the bezel ring.

My intention with this watch was to spend as little as possible on parts not already in my possession and a key consequence of that was a decision to fit a double-domed sapphire crystal rather than the standard tempered mineral flat (because I have none of the latter). I’ve found, as I age, that I tend more towards conservatism in my choices, preferring to preserve as much of the original aesthetic as I can, but at the same time, the double-dome look with these watches has an undoubted appeal. A brief tussle with my conscience concluded, it was in with the gaudy crystal and we can assess the extent to which I’ve made an ill-judged choice.

The last hurdle is to identify a suitable insert to partner the replacement bezel ring. The latter is sourced from my stash but the insert, as with the last 700B I worked on, would come from a Pepsi SKX009. My search located an insert very quickly but from a seller located in Australia. The price was fine though and aside from the crown gasket, has been the only part needing to be purchased specifically for this project.

There is a problem though and that is that the modern SKX inserts are a little on the large size to fit 6309/7548 bezel rings and need their diameter reducing.

In the past, I will have done this by rotating the insert by hand against some fine grained sandpaper until its diameter was sufficiently reduced. However, this technique will never result in a perfectly even reduction and can leave an untidy finish to the edge. This time, I fitted the bezel ring to the chuck of a micro lathe and reduced the diameter in a far neater and more precise fashion. With that done, the bezel ring goes on and the insert snaps in with no drama.

The end result on a spare vented rubber strap I think is effective.

The only real problem for me is the choice of a double domed crystal.

It was a choice of convenience but it leaves a nagging doubt that I’ve ended up with something slightly less genuine, straight and honest than I started with. This one may need revisiting and so watch this space.

Postscript

Well, that didn’t last long. That bloody sapphire crystal has driven me to distraction with its confounded reflections, conspiring activity to obscure not only the view of the dial but to disguise the fact that the dial is blue. There is only one option that any self respecting advocate of the ‘originality is best’ camp would take and that is to install a correct, flat, tempered mineral crystal complete with frosted bevel. And while we are at it, let’s fit a straight vented blue Italian rubber GL831 facsimile strap.

I have Sieko 7548-700b from new 1982,alas during battery change lost one battery retaining strap screw. Having tried various commercial supply sources I am unable to buy said item because I am not in trade. Have you any ideas where I can aquire this screw. Regards TERRY

They do sometimes come up on eBay, not always at reasonable prices! Some watch materials houses may have stock but not in the UK. It is probably a matter of biding your time and keeping your eyes peeled I’m afraid.